Introduction Flashcards
Name some mechanisms of protocols
- addressing and naming
- Fragmentation
Re-sequencing - error control
- flow control
- congestion control
- resource allocation (buffers)
- multiplexing: combine higher-layer sessions into one channel
- compression
- privacy and authentication
What is network coding?
(Hourglass figure)
Nodes combine packets from different sources and generate groups of encoded packets.
A single modified packet is transferred between a potential bottleneck link instead of sending two packets.
What is the difference between network coding and traditional routing?
In network coding, the outgoing packet is a arbitrary combination of previously received packets whereas in TRF the payloads are not modified.
What are benefits of layering?
Layers have to manage complexity, no need to reinvent the wheel.
Common functionality.
What are drawbacks of layering?
- Layers may duplicate lower layer functionality
- different layers need same information
- layers might need to look at headers of other layers
What is a layer-2 packet called?
Frame !!
Name 3 link layer multiple access methods
Channel partitioning: time slots/frequencies/code for exclusive use
Random Access: allow collisions and recover if necessary. CSMA(/CD /CA), ALOHA
Turns: Token rings, bluetooth
Why cant ethernet Scale up to very large networks?
- Flat addresses
- no hop count
- missing protocols (e.g. ICMP)
- Fragmentation/Congestion/Error msg?
What is network byte order?
Least significant bit first (stream into NIC)
Why do we need a spanning-tree-protocol?
To break switching loops in networks to prevent broadcast storms (packets traveling forever)
How does the spanning tree protocol work?
Select root bridge: lowest ID
Find shortest paths to root bridge. Disable connections that cause loops.
What are root ports and desginated ports?
Root ports: ports that lead to root
Designated port: active port
